Gas barrier membranes with impressive
moisture permeability are
highly demanded in air or nature gas dehumidification. We report a
novel approach using polyetheramine oligomers covalently grafted on
the carbon nanotubes (CNTs) to engineer liquid-like CNT nanofluids
(CNT NFs), which are incorporated into a polyimide matrix to enhance
the gas barrier and moisture permeation properties. Benefiting from
the featured liquid-like characteristic of CNT NFs, a strong interfacial
compatibility between CNTs and the polyimide matrix is achieved, and
thus, the resulting membranes exhibit high heat resistance and desirable
mechanical strength as well as remarkable fracture toughness, beneficially
to withstanding creep, impact, and stress fatigue in separation applications.
Positron annihilation lifetime spectroscopy measurements indicate
a significant decrease in fractional free volume within the resulting
membranes, leading to greatly enhanced gas barrier properties while
almost showing full retention of moisture permeability compared to
that of the pristine membrane. For membranes with 10 wt % CNT NFs,
the gas transmission rates, respectively, decrease 99.9% for CH4, 94.4% for CO2, 99.2% for N2, and 97.9%
for O2 compared with that of the pristine membrane. Most
importantly, with the increasing amount of CNT NFs, the hybrid membranes
demonstrate a simultaneous increase of barrier performance and permselectivity
for H2O/CH4, H2O/N2, H2O/CO2, and H2O/O2. All these
results make these membranes potential candidates for high-pressure
natural gas or hyperthermal air dehydration.